Synergy
by bravevulnerability
Summary: "Okay, Castle. Remind me how it feels when we work together." An insert for 7x11, Castle P.I.


**A/N: An insert for 7x11 (Castle, P.I.) that explores the possibility of what could have happened in Castle's new office if Beckett's phone had failed to ring and interrupt them. As usual.**

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><p><em>synergy: <em>

_(noun)_ _the potential ability of individual organizations or groups to be more successful or productive as a result of a merger._

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><p>Theorizing with her is always such a turn on. The change of location from the precinct to his P.I.'s office doesn't alter that in the least and he's missed her. Of course, they still see each other every day, every night, but he misses heading to work together, misses chasing down killers and solving crimes at her side, and maybe him working as a P.I. isn't the most conventional way to recapture this form of their partnership, but if the heated look in her eyes is any indication, she's missed this too.<p>

But then realization flashes in Beckett's eyes, which have fallen to his lips, subduing the flames, and she takes a regretful step back.

"I'm sorry, Castle. We shouldn't be doing this."

"Doing what?" he questions, lowering his voice to a near husk that he knows can have her hot and bothered within seconds

"This. You, me, theorizing - together." She's babbling and despite the words spilling from her lips, he can tell she wants to defy them, wants to do the exact opposite of what she's saying they shouldn't be doing. "It's just - it's not right, especially here after this whole P.I. thing-"

"No, shh, don't. Don't think about it," he coaxes, drifting in closer and silently rejoicing when she doesn't make a move to skirt his touch, her lower lip becoming trapped between her teeth instead. "Just think about how it feels when we work together. Besides, we have the place to ourselves, who's going to know?"

A soft, wanting sound leaves her lips, and oh, he has her. The flames of lust and anticipation are back in her eyes as they flick between his gaze and his mouth, her tongue slipping free to wet her bottom lip.

"Yeah," she concedes on a breath, canting forward the moment he lays a hand to her waist.

"Yeah?" he echoes, watching with renewed excitement as her head bobs up and down in a nod of agreement.

Her hands slide up along his chest, pushing without much force, but enough to have him walking backwards. Castle grunts when she uses his body to shut the door to his office, slamming him up against it with a wicked smirk curling along her lips.

"Okay, Castle," she hums, coiling her fingers around the collar of his shirt and rocking her lower body into his, bumping their hips and sending an arrow of heat straight to his groin. "Remind me how it _feels _when we work together."

That's all it takes for him to haul the lithe line of her body into his, swooping down the short distance it takes to capture her lips and wasting no time in seeking entrance, shoving his tongue past her already opened mouth.

The low hum of her moan fills his office as his thigh slips between hers and the hands on her waist drag her forward, allowing her to indulge in the friction the hard muscle between her legs provides.

Kate tries to shrug her coat off, but her hands keep falling to his waist, fingers occupied with the work of undoing his belt, so he helps rip the expensive fabric from her shoulders, tossing it towards the chair Nicole Morris had occupied only moments before. His belt hits the floor next, his suit jacket too, and he pushes her shirt up until he reaches her breasts, stealing a moment to tug her bra out of the way, cup her in his palms and pinch her nipples between his fingers.

She whines, a familiar, impatient noise that gets caught in the back of her throat, and she lifts her arms over head, pulls the blouse off for herself and slings it in the same direction her coat had gone.

He takes her off guard when he spans a hand at the flat expanse of her stomach, feeling her breath hitch in her chest while he unbuttons her slacks and slips his hand past the waistband of her underwear.

She moans again when he cups her, burying her face in his neck and sucking on the skin stretched across his galloping pulse.

"You're so wet," he growls, can't help stating the obvious, because he knows it's more than the arousing round of theorizing that's gotten her to the point where her underwear are nearly soaked. "Me working as a private investigator turns you on, doesn't it, Beckett?"

Kate nips at his skin – he would bet money she's already left a mark – but doesn't answer, raising her head and taking his lip between her teeth instead. It's answer enough.

Castle fumbles at his back for the lock above the doorknob, ensuring their privacy, before urging her backwards. Her roaming hands beneath his shirt and his bruising grip on her hips keeps her from stumbling in the black leather boots that have her at eye level with him.

"Where do you want to do this first?" he pants out as they bump into the edge of his desk.

Her eyes flash up from the buttons of his shirt, where she's finally managed to unfasten them all without ripping his shirt apart.

"_First_?" she echoes, her voice already so ragged with sex and tinted with amusement. "Castle, we don't have time for multiple rounds here."

"Is that a challenge, Detective?" he counters, and he so hopes it is, because he could have her on at least three different surfaces of this office in record time if that's what she wants.

She pins her swollen lip between her teeth and shoves him back, towards the office chair behind his desk. "We'll see."

They work together to unzip her boots and kick off his shoes. Castle yanks the pants down her legs while she jerks at his until all that is left are his boxers and her matching set of black lace lingerie.

"Cruel," he huffs, hauling her forward by her hips and nipping at her breast through the thin lace of her bra.

Kate mewls, but cards her fingers through his hair, holding him there as she arches into his mouth.

"Am not, you saw me put it on," she reminds him, groaning when he laves his tongue over her covered flesh, the added friction of rough lace scraping over her nipples and heightening her pleasure.

"That's why it's cruel," he explains, panting harshly against her skin before finally pulling back to draw her underwear down her legs. "Because I knew what you were wearing beneath your clothes this whole time and I haven't been able to do anything about it. At least at the precinct, I could have taken you in a supply closet."

Kate pinches his ear for that, but not hard enough to distract him from unhooking her bra.

"That was one time and I told you never again," she mutters as he lifts his hips while her hands coil around the waistband of his boxers and glide them down. "Now stop talking."

He smirks, but complies in favor of curving his hands at her sides, guiding her into his lap and dropping his head back against the cushioned head of the chair when her fingers twine around his erection. Her eyes are black as they stare down at him, her irises nothing more than thin, golden circles of light surrounding the dark pools of her pupils, and she releases an exhale that sounds more like a whimper when she finally sinks down, taking his pulsing length inside the scalding heat of her.

Her thighs clench against his and her arms band around his neck, cradling his head, and he paints his lips along the ridge of her collarbone and the smooth pillar of her neck, burying his moans in her skin as she sets a rhythm, riding him slowly at first before picking up the pace.

His hips buck to meet her in response, driving upwards just as she grinds down, and pulling a strangled noise from her lips when he manages to graze her clit with every stroke. Castle tangles his hand in her hair, surges up to steal her mouth, to swallow the sinful sounds falling from her parted lips, using his free hand to splay his palm at the base of her spine, sealing their bodies even tighter together. Her hips roll harder, faster, and it's too much, too much for him to see past the stars blinding his vision and the pleasure stealing his breath.

They crash into each other like waves until the tide takes them under, the white-hot swell of release drowning them both. Kate seizes over him as he comes, her muscles clamping hard and hot around him just before she collapses forward, gasping against the sweat slicked skin of his heaving chest.

For a handful of moments, he can do nothing more than catch his breath and cradle her sated body against him, tracing the bowed line of her spine out of habit and grazing his lips over her temple.

Until his eyes land on the littered surface of his desk.

She's panting, still riding the waves of her orgasm, and he is too, but he uses his quivering leg muscles to lift from the chair, slowly slipping out of her as he deposits her atop the desk.

"Castle, what are you doing?" she breathes, her chest heaving with every word.

"Just lie back," he instructs, watching with undisguised fascination when her body bends backwards with ease, glorious, damp skin covering the entirety of his desk and spreading across his files.

He leans over her, pressing his mouth to her stomach first, trailing his lips across the taut muscles of her abdomen, nipping gently just to feel her body jerk and shudder beneath him, and traveling higher, dragging his tongue and hot, open mouth along her ribs, up to her breasts.

She keens, loud and breathless, when he takes her nipple in his mouth, swirling his tongue around the stiff peak and adding a scrape of his teeth that always has her spine arching before transferring to her opposite breast, providing it with the same attention.

"Cas - Rick - time-"

"Your phone hasn't rung," he mumbles, lips brushing her sensitive, flushed skin, eliciting a shiver he can feel beneath his mouth. "You've got time."

"But, I-"

His fingers dip between her legs, sinking into the fresh pool of wetness already forming there, and they both groan at the touch, can't help it. He loves how responsive she is, how easy it is for him to get her worked up again so quickly, and he wishes she had the day off so they could spend the entire day christening his desk in every way imaginable.

"I've got time," she gasps, hips rocketing from the desk when he glides two fingers inside her and places his thumb to her clit, already starting a slow but hard circling rhythm.

Castle smears a kiss to her neck, plunging his tongue in the hollow of her throat, before his mouth migrates back down the path of her body, taking the time to suckle and tease the valleys of flesh and ridges of bone, coaxing her to the precipice of release and then withdrawing his fingers from between her legs.

Beckett groans in displeasure, one of her hands fisting in a file on his desk, crinkling the paper, while the other finds his shoulder, scores him with her nails. She's cursing him under her breath, but he doesn't make her wait long, dropping back into his office chair and drawing her legs up to rest over his shoulders.

Her spine arcs, her body snapping into a serpentine shape at the touch of his mouth to her core while his hands roam from her thighs, up to span across her stomach. She grasps his wandering hands within seconds, tugs him by the fingers until his palms can splay over her breasts, and he grins, flicking her clit with his tongue.

He takes his time, exploring and tasting every well known inch of her and the remnants of what they'd done, but he has her coming undone in only a few short minutes, just in time to hear her phone ringing.

"Fuck," she croaks, missing the call.

For a few seconds, she can't move, limp and sated atop his desk, and Castle carefully untangles her legs from around his neck and shoulders, scraping his teeth along her thigh, sinking his teeth into her calf muscle.

"We could go again," he muses, knowing that she'll refuse, but the sharp intake of breath he hears her take, the still sparking aftershocks shaking her body at each graze of his fingers to her cooling skin tell him that she wishes they could.

Her phone starts to ring again and she sighs, but he rises, hunts down the vibrating device in her wrinkled dress pants beneath the desk and hands her the phone before the call can be sent to voicemail again.

To her credit, when she answers Esposito's call, her voice is steady, even while he hovers above her, lazily stroking his tongue along the sensitive spot behind her ear.

"Okay, bring him in," she says to Espo, pushing up on her elbows and dislodging Castle from her shoulder as she ends the call. He helps her into a sitting position on the edge of the desk, revels in the sight of her body as she stretches her arms above her head and snags her underwear from the desk drawer they managed to land in. "I'm sorry, baby. I gotta go."

He scoffs. _Baby. _She's been calling him that a lot lately, at home in front of his mother and daughter and in bed (but he has to admit, he can't get enough of it when she's moaning the pet name in his ear while they're tangled in the sheets), and though he usually shoots her a glare for it, his curiosity overwhelms his feigned annoyance at the term of endearment.

"Bring who in?" he asks instead while she slips into her pants and he considers hiding her bra from her, coercing her into sharing the latest information Esposito's delivered over the phone, but he decides to play the role of good husband and retrieves the lingerie from the ground.

She offers him a smile for it and hops down from his desk, gathering the rest of her clothes from the chair while he steps into his boxers and tugs his pants back on.

"You're really not going to tell me anything?" he demands incredulously, following her across the room. "After everything we just did?"

"Castle," she huffs, sliding her shirt on, but he twines his arms around her before she can don her coat, pins her to the nearest wall with his hips.

"Fine, Beckett, I see how it is," he murmurs, allowing her to feel the hard length of him against her stomach.

Subtle guilt flares in her eyes and that's not what he wants, not really. It isn't her fault they can't work together, but it doesn't mean he can't punish her, just a little.

Castle presses a kiss to her mouth, tracing the seam of her lips until she tentatively opens for him, her fingers drifting up to curl in his hair at the prominent taste of herself on his tongue.

"Mm, I promise I'll make it up to you," she mumbles around his mouth, trailing a hand between them to brush her knuckles over the bulge inside his pants.

He grits his teeth against the jolt of electricity her touch sparks and draws her hand away from his crotch, smudging a final kiss to her lips before she can pull away and head for the door.

"Just remember, Beckett, It's so much more satisfying when we work together."

Kate shoots him a heated look over her shoulder that really does nothing to help the growing problem between his legs.

"Believe me, Castle, if it was up to me, we'd be solving this case together," she assures him, sincerity and a lingering hint of yearning that's been hiding there for the last few weeks shimmering in her eyes, but it only takes a moment for the flicker of arousal to return. "You just proved exactly how great it feels to work with you."


End file.
